[collectd] Bug#590656: collectd: apache traffic cut off at 1 GBit/sec

[Sebastian Harl]

Hi,

On Wed, Jul 28, 2010 at 08:47:59AM +0200, Carsten Otto wrote:
> When apache (httpd) does more than 1 GBit/sec of traffic, the RRD file
> does not contain these values. I assume there is some maximum defined at
> 1 GBit/sec and/or some overflow occurs. My server does 1,5 GBit/sec in
> average, so the graph currently is useless to me.

Right, the maximum value for the "apache_bytes" type is set to 1 GiBit
(per second). RRDtool will consider any higher values as invalid and
store "UNKNOWN" instead. I'm not sure what amount of traffic Apache is
(currently) able to handle but with 10 GiBit connections becoming
increasingly common, I think this limit should be raised to at least
that value.

Also, other data types could possibly be "affected" in a similar way.
The reason for setting max. values in the first place is to avoid huge
peaks in case of a counter reset (e.g., after restarting some service).
In the future (collectd 5), this will probably be handled by using the
"DERIVE" data type rather than "COUNTER" in the RRD files. In the
meantime, I think we should raise the limits.

Florian, do you agree with this?

As a work-around for now, you can do the following:

 * Change the max. value defined in /usr/share/collectd/types.db (see
   the types.db(5) manpage for details) -- this will make sure RRD files
   created in the future will have the right max. value.

   However, note that this file will be overwritten on the next upgrade.
   So, a somewhat better approach would be to create a new, custom
   types.db file (e.g. /etc/collectd/types.db.local) and add a custom
   definition for "apache_bytes" which will then overwrite the default.
   Then, add the following line to your collectd.conf:

     TypesDB /usr/share/collectd/types.db /etc/collectd/types.db.local

   (The custom types.db has to be specified after the default!)

   (You'll then get a "notice" message in the log on startup saying
   "Replacing DS `apache_bytes' with another version.", which, obviously
   can be ignored.)

 * "tune" any existing "apache_bytes" RRD files using something like

     rrdtool tune $file --maximum count:$new_max

   See the rrdtune(1) manpage for details.

HTH,
Sebastian

-- 
Sebastian "tokkee" Harl +++ GnuPG-ID: 0x8501C7FC +++ http://tokkee.org/

Those who would give up Essential Liberty to purchase a little Temporary
Safety, deserve neither Liberty nor Safety.         -- Benjamin Franklin

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